Semiconductor device fabrication is the process used to create the integrated circuits that are present in everyday electrical and electronic devices. In typical semiconductor fabrication, integrated circuits (“ICs” or “chips”) are built in large quantities on a single large wafer of semiconductor material, typically silicon. The individual chips are patterned with small pads of metal near their edges that serve as connections to a mechanical carrier. The chips are then cut out of the wafer and attached to carriers, typically via wire bonding such as thermosonic bonding. The wires used in the wire bonding eventually lead to pins on the outside of the carriers, which are attached to circuitry making up the electronic system.
A flip chip pin grid array (FCPGA) is a form of pin grid array in which the die faces downwards on the top of the substrate with the back of the die exposed. The term “flip chip” can also refer to a controlled collapse chip connection which is a method for interconnecting semiconductor devices, such as IC chips and microelectromechanical systems (MEMS), to external circuitry with solder bumps that have been deposited onto the chip pads. The process is similar to conventional integrated circuit fabrication, but includes a few additional steps. Toward the end of the manufacturing process, attachment pads are metalized to make them more receptive to solder. Metalization typically includes several treatments. A small dot of solder is deposited on each metalized pad. The chips are then cut out of the wafer. To attach the flip chip into a circuit, the chip is inverted to bring the solder dots down onto connectors on underlying electronics or a circuit board. The solder is then re-melted to produce an electrical connection, typically using a thermosonic bonding, or alternatively, a reflow solder process.
During production, individual semiconductor chips are typically oriented such that their leads face away from the receiving surface. It may be necessary to “flip” the chips with a flipping mechanism before the chips are transferred for subsequent processes, such as function testing or visual integrity checking. Conventional flipping mechanisms increase the frequency by which the semiconductor packages are picked and placed, which increases the likelihood that packages are dropped and/or damaged.
For example, FIG. 1 depicts related art in which a pivoting part 3 is used for detaching individual semiconductor chips from a wafer or from its substrate 1 by means of a die ejector 2. The pivoting part 3 enables a flip head 5 to swivel by virtue of a pivotal point 4. A pickup element 6 is arranged on the flip head 5 out of an optical connection line 1c between a first optical facility 7 and the wafer surface. The related art shown in FIG. 1 comprises a pickup position 1a for the chip to be picked up and a deposit position 1b for a placing facility 8. The placing facility 8 includes a pickup element 9, which may take the form of a vacuum pipette, in order to place the turned chip within a smart card module, for example, by moving the placing facility 8. This system is impractical for industrial use because it has only one pickup element and relies on a time-consuming sequential method process.
FIG. 2, depicts a device for checking and rotating semiconductor chips according to another related art. The device includes a wafer (not shown) and an associated substrate 11 with a wafer surface 11a, from which individual semiconductor chips are ejected upwards with a die ejector 12 from below. A pivoting part 14 is arranged such that that it rotates in an executed rotation as indicated by arrows 15, 16 about a pivotal point 17, which is arranged above the chip to be picked up. The wafer can be moved with the substrate 11 in an X direction as indicated by arrows 13. The wafer can also be moved in a Y direction.
The pivoting part 14 includes cheek projections 18a and 18b and two opposite pickup elements 19, 20, which may take the form of vacuum pipettes. The pickup elements 19, 20 enable simultaneous picking up and depositing of two semiconductor chips. The first vacuum pipette 19 is configured to pick up a semiconductor chip from the substrate 11, while the pickup element 20 is configured to deposit another semiconductor chip on a placing facility 21. The placing facility 21 may be equipped with a vacuum pipette 22. In operation, the placing facility 21 is moved sideways as indicated by the double arrow 24. At almost the same time, the pivoting part 14 rotates about its pivotal point 17, this time in the opposite direction. After a 90° rotation of the pivoting part 14, an opening (not shown) is created in the pivoting part 14 to form a sight channel 23a. The sight channel 23a runs vertically through the part 14 from a first optical facility 23 to the surface 11a of the substrate 11, which is covered with a wafer of a second semiconductor chip.
This sight channel 23a enables the optical facility 23 to record the step of the second semiconductor chip being picked up on the substrate 11, and enables the surface and position of the second semiconductor chip to be checked. As soon as the pivoting part 14 has finished a 90° rotation followed by a 180° rotation, pickup of the second semiconductor chip is executed by the second vacuum pipette 20. A second optical facility (not shown) may take the form of a die positioned on the fly camera 25 and may be configured to check a flip offset of the previously rotated chip. In the event that there is a flip offset, the second optical facility calculates corresponding correction data and passes the data to the self-adjusting place element 21. The place element 21 then deposits the chip in an indexer 26. The position of the place element 21 is checked by a second camera 27. The device of FIG. 2 uses only two vacuum pipettes to flip the chip, hence the device is only capable of flipping a limited number of units per hour (UPH).
Related art US 20140328652 A1 discloses a transfer apparatus for transferring electronic devices from a wafer to a test handler. The transfer apparatus comprises a rotary device rotatable about an axis and a plurality of holders configured to hold the electronic devices for transfer from the wafer to the test handler. The holders are coupled to, and extendable from, the rotary device to pick the electronic devices from the wafer. Specifically, the plurality of holders are arranged circumferentially around, and inclined with respect to, the axis of the rotary device, so as to change an orientation of the electronic devices on the wafer to a desired orientation of the electronic devices on the test handler. Because the transfer apparatus uses a vertical wafer table, chips are prone to falling from the wafer and becoming damaged.
Another related art, WO 2003058708 A1, discloses a flip bonder having a pick-up turret assembly with a number of pick-up nozzles, and a placing turret assembly with a number of placing nozzles. Each pick-up nozzle picks a die by its bumped surface, and indexes the picked die to the transfer location, thereby flipping the picked die. At the transfer location, the picked die is transferred to a placing nozzle, with die now held by its back surface. The placing nozzle is indexed to a fluxing location where flux is applied to the die, and further indexed to a placing location, where the fluxed die is placed on a target location on a lead frame, with the bumps abutting lead portions of the lead frame. The multiple nozzles allow concurrent operations with each die, thus supporting an improved throughput. However, because there is only one vertical flipper, it is only possible to have one check station.
A need, therefore, exists for a system capable of quickly and accurately picking, flipping and transferring chips without dropping or damaging them. It should also provide increased operation space so that chips can be examined or checked by multiple devices such as cameras.